In this resubmission of our renewal application, funding is requested for continued support ofthe NIEHS Center for Environmental Health Sciences (CEHS) at the Massachusetts Institute of Technology (IVIIT). The overall focus ofthe MIT CEHS is to understand how toxic environmental agents perturb biological systems and to determine how such perturbations may affect human health. The MIT CEHS is led by Professor Leona Samson. The current CEHS membership consists of 36 members derived from a total of eight MIT departments in both the Schools of Science and Engineering, plus three members from Harvard University, specifically the Harvard School of Public Health (HSPH) and the Harvard Medical School (HMS). The MIT departments are Biology, Chemistry, Biological Engineering, Chemical Engineering, Civil and Environmental Engineering, Mechanical Engineering, Nuclear Science and Engineering, Electrical Engineering and Computer Science; the HSPH department is Epidemiology, and the HMS faculty are based at the Brigham and Women's Hospital and the Massachusetts General Hospital. The current Facilities Cores are (i) the Bioanalytical Facilities Core, (ii) the Genomics and Imaging Facilities Core, (iii) the Animal Models Facilities Core, (iv) the Integrative Health Sciences Facilities Core. The services available through the four Facilities Cores include sophisticated mass spectrometry, accelerator mass spectrometry, transcriptional profiling, Solexa sequencing, bioinformatics and robotics, transgenic and knock out animal production, pathology services, state-of-the-art microscopy and imaging, and clinical services for translational research. Other units include the Administrative Core, the Pilot Project Program, the Global Environmental Health Science Program, and the Community Outreach and Education Core (COEC). The Center sponsors a wide variety of enrichment activities including specific seminars in the Biological Engineering departmental seminar series, two CEHS specific seminar series, an annual Poster Session, and several other mechanisms designed to nurture interactions among CEHS members and to promote the activities ofthe CEHS at MIT.